The electron microscope is a powerful tool for investigation of the structure of biological objects. The ultimate structural resolution which can be obtained for most biomolecules is limited by the radiation sensitivity of the object rather than by the instrument itself. For objects which can be arranged in a periodic array, diffraction techniques can be applied which need a significantly lower dose to obtain the same resolution. Unfortunately, most of the interesting biological specimens cannot be crystallized. In these cases it is quite important to elucidate the imaging mode, instrument, and image processing techniques which give maximum information for a given dose of incident electrons. Studies are planned to elucidate the optimum imaging procedure for different types of model objects. The rearrangement of the object and/or dissipation of parts of the object due to destruction of bonds may be largely prevented by embedding the object in material of low atomic number (e.g., beryllium or carbon) and by cooling the object to helium temperatures. Some evidence of its feasibility is given by recent measurements of Dubouchet and Isaacson. The embedding in beryllium seems most advantageous due to its small scattering cross-section resulting in a weak structural noise. However, for thick specimens and objects in an environmental chamber, plural scattering occurs, resulting in a loss of contrast and resolution. To account correctly for phase and amplitude effects on the image formation, we have developed a general theory of image formation on a wave mechanical basis which considers elastic and inelastic electron scattering. The effect of plural scattering will be studied intensively for characteristic model objects. Imaging methods will be determined which reduce the parasitic influence of the plurally scattered electrons as much as possible and which enable us to maximize the information obtainable from biological objects for a given voltage and dose of the incident electrons.